Removing gum-forming components from hydrocarbon distillates



United States Patent REMQVING GUM-FQBMXNG CQMPQNENTS FRiGM n YnnoCAnnpN plsrnnarns Adolf Christiaan van. Beest, Jacobus, Wilhelmus Le Nobel,

Christiaan Bieter van' Dijk, and Fansisclls Johannes,

Fredericus van' der Blas', Amsterdam, ethcrland as- Signo'rs 'to Shell Development Company," Erben/ville',

No Drawins Application December 1 9., 19.552,

` sans; N9'. 32741316 i ,Claims priority, application Netherlands Declllpil': 1951' x tlclim-Si (Q1: 12611-35) rl`his inventionrelates to a method of removing gumforming components from hydrocarbon fractions, e. g., hydrocarbon distillates, particularly cracked gasoline distillates. Y

It is known that hydrocarbon fractions, particularly gasoline fractions obtained by thermal or catalytic cracking, whether in the vapor or liquid phase, of hydrocarbons or hydrocarbon mixtures, contain reactive vunsaturated compounds, such as alkadienes, which, during storage, lead to the formation of gummy substances. The ,formal tion of gumrny substances is acceleratedby` `the inuence of oxygen,`light'and/or heat. Y N

Various refining methods have been proposed for removing the above-mentioned reactive unsaturated coinpounds, which arelgenerally termed gum-forming cornponents. For example, hydrocarbon fractions'are often treated with strong v'sulfuric acid to remove vthese gum: forming components. This treatment, Jho,vveyeryhasP vthe disadvantage that other component's'of the treatedv hydro# carbon fraction, such as allienes and aromatic Fco-mpsounds which possess valuable properties as motonfuelhcomponents, inter alia forr improving antiknock properties, are also attacked by the sulfuric" acid. Removal of the gunnforming components has also been eitectedby treating the hydrocarbon fraction with an'v'dso'roent', such as fullerls earth or bauxite.` Thistreatnentalso removes valuable components together vyith'the undesirable rginnforming components. Other methods proposed toi-'rre moving the guni-formingcomponents includeuoxidizing the gum-forming eornpor'ientswtogun'and th removing the gum from the treated Yhydrocarbon f lon.- ever; it is diicult to separate theres'ulting from the hydrocarbon fraction. A

' ltv is, theretoejaprincipal object of the present inyen; tion to provide an improved method for Vremoviifg for-ming. componentsvtr'ojm hyldr l tactlons, e. 4 distillat'es. l Y furthenobjeotis pr idewan improved method'rfor remoying gurrrtrinng :components 'troni ilydrocarbon distillatls:vithout'also rom 4yl ble componets'present therein'. more l'specific o t yis t@ previsti@ an improved malins? for. ren-.Oy s" su' fn'- inscannen@ fron Cracked seidig@ A' f A ,1 fsllQtu t stalled @eignet-.ibn Y In assitance ititlitllspresent invention, it has non been found that gum-forming components can be I1e nggyed'from hydrocarbon fractions hy-a process which comprises heating a hyrocarbon fraction to a temperallre ,Q @I least 145)? G., and preferably not `(greater:than about 11150.?l in the presence of a hydrocarbon solution of organ-ic peroxides which solution has been formedby heating a hydrocarbon fraotion to a temperatureiofifrom about 75 C. to about l=25' C. underoxidizxingfcdil tions, and maintaining the hydrocarbon fiacvtionatsaid tempera-ture of at least 140? C., and f preferably Ariot greater than about 2509 G., for a p'eriodofftirfrie to convert the gum-forming components thereinto liquid polymers.

According to a preferred embodiment of the invention, gum-forming components are removed from hydrocarbon fractions, particularly cracked gasoline distillates, by heating the hydrocarbon distillate, 'to a temperature of from about C. to about 125 C., and'preferably of from about C. `to about 100 C., under oxidizing conditions, c. g., in the presence of an oxygen-containing gas, for a period of time suticient to torni organic peroxides therein, and further heating the resulting organic peroxide-containing hydrocarbon distillate to atempera; ture of from about 140 C'. to abont' 250 C., and ypreferably of from about 1709 C. to about`200 whereby the gum-forming components therein are converted to liquid polymers.' M According toanother embodiment of the invention, a first hydrocarbon fraction, particularly" a"cracl ted distillate is heated to a temperature of from about C.y to about C., and preferably of from` about 80 C. about 100Dv C., under oxidizing conditions', as in lthe presence of an oxygencontaining gasffor all period nof suicient to form organic peroxides therein, the resulting hydrocarbon "fraction` containing V'organic peroxides with a second hydrocarbon fraction, partlcu-V larly a gasoline distillate, fijorn vhi'ch gumlforming c ponentsare A t'o be removed, and maintaining the resul mg acimixture at a temperaturehof from about Cfto about 250C., and preferably pfjfrqni apprit 170 'C'. te abont 2009 C., for a periodof ltime Asuicifili i0 ,COllYert the gum-'forming' components inthe second hydrQcarbon fracties to liqna ply'iae'fs. l "i112 pros''f'the piseut invention is particularly important vfor lremoving;unsat'urated com pnouridsY as aliladienes, 'which leadr tox the yformation opf'gulm, ,from hydrocarbon listin tes' when con in, in y: iqdititm te the gom-forming"unsaturatedy 'componnds Va considerable amount of rother types rof unsaturated compounds, alltenes, which possess, properties extremely die motor fuels.Y `xarnples hydrocarbon A, are gasoline ,fractions''obtained` by crackingy or ing 'hydrerbon'sur hydrecar'bon rsjshale', s and lignite tar oils. The present process lis also applil cable `to uthe""treatmenttot mixtures of" d iilerent hydrocarb'oribils, sufcfra a'mixtnr'e of a cracking distillate a' misfit-nnanche@" ny ne 'been avec it possiblen't relnoye the undesirablefgumtorming {com} Paenjts wehen adversely Csm-. l oil' in` ythe processare x l edingly sligf lrftliis process, the gum orming components at@ 0,11: vetted into liquid polymers. instead of into gur; iS"a1`` imrtait advantage" fesingiiggn pslymerlfr. distillate Ais -more'jeas'ly ,en en 'than these lfrom the hydrocarbon ,c listillate.l Althoughthe fn'ehnisln Qf i119 t;irrna'tlcni Qf'lianid ppl-ynir from $1.16 fS` @nel h dstn' y ascertained.. 1Q Pernis-MCS .Originally iornied- 'bing 'abonf'pblymerizatigni rhaps also. telomerization, as the gnnfornifing Components .rig aas, 'such as oxygen. air, .Ozone 'Played in the @gronde fennetiLQn step- Ths' am Qf'px'ygsn n sd wil-1 vary widely @Werding in th@ sus y of' .csfnppnnds present the hydrocarbon fractionfyyhich are ,capable of conversion intoperoxides, and also to the n Vture of-,thesec0n1p9unds- In general, the amont of iiyssn employed willvrange bet', Vn about 0.1 and ab ut byweight based onthe it@ frac:

either be previously dissolved in the hydrocarbon fraction or be injected into the hydrocarbon fraction during the heating step. In the latter case, it is recommended that, in order to promote the formation of peroxides, as intimate as possible a distribution of the oxygen in the hydrocarbon fraction should be insured by means of intensive mechanical contact. The optimum temperature range for the formation of the peroxides is from about 75 C. to about 125 C., particularly from about 80 C. to about 100 C. Generally, the hydrocarbon fraction is maintained at this temperature for a period of time of from about l minute to about 2 hours.

The rate of formation of the peroxides can be increased by adding a small amount of preformed peroxides to the hydrocarbon fraction to shorten the induction period. The same effect can also be achieved by continuously carrying out the formation of peroxides, e. g., in a vessel fitted with an agitator orin a tubular reactor, and recycling a part of the peroxides formed to the point at which the hydrocarbon fraction is supplied.

In order to prevent the peroxides formed from decomposing before they are used for initiating the polymerization reaction, in which gum-forming components are converted into liquid polymers, it is recommended that the polymerization reaction be carried out as soon as possible after the peroxide formation.

The duration of the second stage of the treatment, in which conversion of the gum-forming components into liquid polymers takes place, depends on various factors, such as the temperature of the treatment, and the quantity of gum-forming components present. The optimum temperature range for the conversion of the gum-forming components into liquid polymers is from about 140 C. to about 250 C. and particularly from about 170 C. to about 200 C. If desired, temperatures higher than 250 C. can be employed, but temperatures at which thermal polymerization and cracking of the hydrocarbon oil begin to occur should be avoided. Best results are obtained by maintaining the hydrocarbon distillate at the elevated temperature for a time of from about 1 minute to about 2 hours. In some cases, conversion can even take place within 1 minute.

If desired, both the formation of the peroxides and the conversion of the gum-forming components can be accomplished in the presence of ultra-violet light which accelerates both reactions.

When the temperature of peroxide formation or conversion of gum-forming components to liquid polymers is above the boiling point of the hydrocarbon oil being treated, it is necessary to carry out the treatment under pressure. The application of pressure during the peroxide formation is desirable since it makes possible a higher concentration of oxygen in the hydrocarbon oil, as a result of which the rate of formation of peroxides is accelerated.

The liquid polymers formed from the gum-forming components are preferably removed from the hydrocarbon oil by distillation. This distillation will be carried out at atmospheric pressure or at a reduced pressure, depending on the nature of the hydrocarbon oil. If desired, the hydrocarbon oil can be freed from traces of aldehydes and ketones, formed simultaneously with peroxides, by washing the hydrocarbon oil with a saturated aqueous solution of sodium bisulte, prior to the distillation step. After this washing step, and after the separation of the hydrocarbon oil from the aqueous layer, a small amount of concentrated potassium or sodium hydroxide can also be added to the hydrocarbon oil to neutralize any acidic components, prior to the distillation step. The liquid polymers can also be removed from the treated hydrocarbon oil by the use of an adsorbent, such as clay, bauxite, silica gel and fullers earth.

According to the preferred embodiment of the invention, the hydrocarbon oil to be treated, preferably a cracked gasoline distillate, is rst heated to a temperature of from about C. to about 125 C., preferably from about C. to about 100 C. under oxidizing conditions, and for a period of time suicient to effect the formation of organic peroxides therein, the thus-treated oil is then heated to a temperature of at least 140 C., preferably of from about 170 C. to about 200 C., and maintained at this temperature for a period of time suiicient to Vconvert the gum-forming components therein to liquid polymers, and the liquid polymers are removed from the treated hydrocarbon oil. This treatment can be carried out either in a batch or continuous type operation. When operating continuously, the hydrocarbon oil is gradually transferred from a vessel maintained at a temperature of 75-125 C. into a vessel maintained at the temperature required to convert the gum-forming components into liquid polymers. The throughput rates in both vessels should be regulated in such a way that the residence time of the hydrocarbon oil in both vessels is suiicient to effect formation of the peroxides and to convert the gum-forming components to liquid polymers. The oxygen-containing gas which is required for peroxide formation can either be dissolved beforehand in the gasoline, or it can be injected at reqular intervals into the vessel in which peroxide formation takes place.

According to another embodiment of the invention, a first hydrocarbon oil, preferably a cracked distillate, is heated to a temperature of from about 75 C. to about C., preferably from about 80 C. to about 100 C., under oxidizing conditions, and for a period of time sucient to effect the formation of organic peroxides therein, the resulting hydrocarbon solution of organic peroxides is then admixed with a second hydrocarbon oil from which gum-forming components are to be removed, preferably a cracked gasoline distillate, the resulting admixture is maintained at a temperature of at least about C., preferably C.200 C., for a period of time sucient to convert the gum-forming components in the second hydrocarbon oil to liquid polymers, and the liquid polymers are then removed from the treated hydrocarbon oil. The second hydrocarbon oil can be identical to the first hydrocarbon oil. It is most advantageous to employ, as the rst hydrocarbon oil, one which contains a relatively large amount of peroxide-forming components, in order to obtain a solution containing as high as possible a concentration of peroxides. It is preferred to add the solution of peroxides in the rst hydrocarbon distillate gradually to the second hydrocarbon distillate so that the peroxides are added to the second distillate in the proportion in which they are used to convert gum-forming components to liquid polymers. This method of operation prevents the formation of a relatively high initial concentration of free radicals from the peroxides, which free radicals might react upon each other and consequently not be used for initiating the desired polymerization re action. The gradual addition of the solution of peroxides to the second hydrocarbon oil is of particular importance when the solution contains a relatively high concentration of peroxides.

It is advisable that the second hydrocarbon oil be previously raised to such a temperature that, after it has been mixed with the solution of peroxides in the first hydrocarbon oil, the mixture will be at the temperature required for converting the gum-forming components to liquid polymers.

The treating process of the present invention is most advantageously carried out at the cracking plant (either the thermal or catalytic cracking plant) at which the hydrocarbon distillates to be treated are obtained. For example, peroxide formation is effected in a cracked distillate, when this is still in the plant, by supplying an oxygen-containing gas to a suitable place in the cracking plant, that is, to a place where the cracking product is at a temperature of 75-125 C. The resulting hydrocarbon distillate containing organic peroxides is then heated to the temperature required to convert the gum-forming components therein to liquid polymers. Alternatively, ahy-V drocarhon:V distillate containing peroxides which. havebeen formed-by heating the hydrocarbon distillate to a temperature of 75.-1125'? C. under oxidizing conditions, can be Supplied to a place in the. cracking. plant where, the crack ing products are at a temperature of at least 140 C., preferably 176)?200? C., toetect conversion of the gumforming components in the cracking products to liquid polymers.

The inventionr is illustrated by the following examples:

Example I The initial material was a cracked gasoline, Qbtained by thermally cracking solid paraffin wax. This gasoline had a boiling range of 4l-131 C. and an M. A. number of 36 (M. A. number is an abbreviation for maleicacidanhydride number, which is a measure of the number of conjugated double bonds in the oil). The gasoline was heated for lVz hours at 110 C. in an autoclave, 0.2% by weight of oxygen being added. After this treatment the content of peroxides in the gasoline amounted to 90 mg. aeq./litre (the initial gasoline contained no peroxides), while the M. A. number had undergone practically no change.

Then the gasoline was quickly heated up to 170 C. and maintained at this temperature for 11/2 hours. After this treatment, the peroxide content of the gasoline had dropped to 0.2 mg. acq/litre, while the M. A. number of the gasoline had dropped to l1.

Example Il The initial material was a gasoline with a boiling range of 55-140 C., obtained by the catalytic cracking of a Venezuelan gas oil. The gasoline had a content of alkenes of 53% by Weight, and a content of alkadienes of 1.3% by weight.

This gasoline, together with a quantity of 2.5% by weight of gaseous oxygen, based upon the gasoline, was heated in an autoclave to 100 C. and maintained for 30 minutes at this temperature. At the end of this treatment a quantity of peroxides of 90 mg. aeq./litre had formed in the gasoline, while the content of alkenes and alkadienes had undergone no change. The peroxidescontaining gasoline thus obtained was then quickly heated in the same autoclave to 180 C. and maintained at this temperature for 30 minutes. At the end of this treatment the gasoline was found to contain no peroxides. The content of alkenes remained practically the same,

- while the content of alkadienes was reduced to 0.3%

by weight.

The gasoline was then washed with a saturated aqueous solution of sodium bisulphite, to remove traces of aldehydes and ketones which had formed in the gasoline during the oxygen treatment at 100 C. for the formation of the peroxides. After the gasoline had been separated from the aqueous solution, a small quantity of a 30% aqueous sodium hydroxide solution was added to the gasoline, so as to remove any acid components which might be present. Finally the gasoline was distilled, the polymerization and condensation products formed from the gum-forming components remaining as residue.

ln this way a yield was obtained of 97.5% by weight, based upon the initial gasoline, of a rened gasoline which was free from peroXides and, in consequence of its very low contents of alkadienes, had a considerably better storage stability with respect to gum-formation than the initial gasoline.

Example III The initial material was a gasoline with the boiling range 70-140 C., obtained by the catalytic cracking of a Venezuelan heavy gas oil. The gasoline had an alkenes content of 53% by weight and an alkadienes content of 1.3% by weight (corresponding to an M. A. number of 13), the remaining components of the gasoline beingxsaturated: hydrocarbons. After the. addition of 0.003%. by weight ofl p=phenylenediamine thg gasoline had an :induction period of 200 minutes, determined according to the relevant- A. S. T; M. test- The gasoline was fed continuously through an auto.- olave fitted with an agitator, into which Oxygen was simultaneously introduced. Thetemperature inthe auto.- clave was 85 C. The throughput rate was so regulated that the average time the gasoline remained in the autoclave was 10 minutes. At the outlet? of the autoclave the gasoline had a peroxides content of 119. mg. acq/litre (the initial gasoline contained no. peroxides. at all), while the content of alkenes and alkadienes had undergone no change. y

The gasoline containing peroxides thus obtained was f then conducted continuously through a second autoclave with an agitator. This autoclave Was maintained at 180 C., and the residence time of the gasoline was 13 minutes.

The gasoline discharged from the second autoclave was washed with a saturated solution of sodium bisulphite and then distilled, after the addition of a small quantity of a 30% aqueous sodium hydroxide solution. Distillation was continued until a gasoline was obtained as distillate which had the same final boiling point (140 C.) as the initial gasoline. The distillation resulted in 4% by weight of liquid polymers being left as residue, while 96% by Weight (based upon the initial gasoline) of refined gasoline was obtained, which was free from peroxides and had an M. A. number of 4, an alkenes content of 53% by weight, and an alkadienes content of 0.4% by weight. After the addition of 0.003% by weight of p-phenylenediamine the induction period of the gasoline proved to have increased to 750 minutes.

We claim as our invention:

1. A method of removing gum-forming components from a cracked gasoline fraction which contains a substantial proportion of alkenes and appreciable proportions of alkadienes and gum-forming components, which comprises heating the cracked gasoline to a temperature of from 75 C. to 125 C. and maintaining it at that temperature in the presence of a minor amount of oxygen for a period of time sucient to etfect the formation therein of at least about milligram-equivalents per liter of organic perioxides but insufficient to reduce appreciably the alkadienes content of the gasoline, immediately thereafter heating the resulting peroxide-containing cracked gasoline to a temperature of from about 170 C. to about 200 C. and maintaining it at that temperature for a time sutiicient to substantially reduce the peroxide content and the alkadiene content of the gasoline and to produce liquid polymers from the gum-forming cornponents but insulicient to materially reduce the alkenes content of the gasoline, and subsequently distilling the thus-treated cracked gasoline to separate the gasoline components from the liquid polymer as a higher boiling material.

2. The method in accordance with claim l, wherein the rst heating for the formation of the organic peroxides is at a temperature of from about 85 C. to about C. and from about 90 to about 119 milligramequivalents per liter of organic peroxides are formed and wherein the second heating for the reduction in peroxide content and formation of liquid polymer is at a temperature of from about C. to about 180 C.

3. The method in accordance with claim 1, wherein the cracked gasoline is a catalytically cracked gasoline containing about 53% by Weight alkenes and about 1.3% by weight alkadienes and wherein the temperature of the rst heating is about 100 C. and of the second heating is about 180 C.

4. A method of removing gum-forming components from a cracked gasoline fraction which contains a substantial proportion of alkenes and appreciable proportions of alkadienes and gum-forming components which comprises heating a first cracked hydrocarbon fraction containing peroxide-forming components to a temperature of from 75 C. to 125 C. and maintaining it at that temperature under oxidizing conditions and for a period of time sufficient to eiect the formation of organic peroxides therein, admixing the resulting hydrocarbon solution of organic peroxides with said cracked gasoline fraction and heating the resulting mixture to a temperature of from about 170 C. to about 200 C. and maintaining it at that temperature for a time suflicient to substantially reduce the peroxide content and the alkadiene content of the mixture and to produce liquid polymers from the gum-forming components there- V8 of but insufficient to materially reduce the alkenes content of the gasoline, and subsequently distlling the thustreated mixture to separate the gasoline components thereof from the liquid polymers as a higher boiling material.

References Cited in the le of this patent UNITED STATES PATENTS Youker May 23, 1933 Martin et al May 28, 1935 OTHER REFERENCES 

1. A METHOD OF REMOVING GUM-FORMING COMPONENTS FROM A CRACKED GASOLINE FRACTION WHICH CONTAINS A SUBSTANTIAL PROPORTION OF ALKENES AND APPRECIABLE PROPORTIONS OF ALKADIENES AND GUM-FORMING COMPONENTS, WHICH COMPRISES HEATING THE CRACKED GASOLINE TO A TEMPERATURE OF FROM 75* C. TO 125* C. AND MAINTAINING IT AT TEMPERATURE IN THE PRESENCE OF A MINOR AMOUNT OF OXYGEN FOR A PERIOD OF TIME SUFFICIENT TO EFFECT THE FORMATION THEREIN OF AT LEAST ABOUT 90 MILLIGRAM-EQUIVALENTS PER LITER OF ORGANIC PERIOXIDES BUT INSUFFICENT TO REDUCE APPRECIABLY THE ALKADIENES CONTENT PEROXIDE-IMMEDIATELY THEREAFTER HEATING THE RESULTING PEROXIDE-CONTAINING CRACKED GASOLINE TO A TEMPERATURE OF FROM ABOUT 170* C. TO ABOUT 200* C. AND MAINTAINING IT AT THAT TEMPERATURE FOR A TIME SUFFICIENT TO SUBSTANTIALLY REDUCE THE PEROXIDE CONTENT AND THE ALKADIENE CONTENT OF THE GASOLINE AND TO PRODUCE LIQUID POLYMERS FROM THE GUM-FORMING COMPONENTS BUT INSUFFICIENT TO MATERIALLY REDUCE THE ALKENES CONTENT OF THE GASOLINE, AND SUBSEQUENTLY DISTILLING THE THUS-TREATED CRACKED GASOLINE TO SEPARATE THE GASOLINE COMPONENTS FROM THE LIQUID POLYMER AS A HIGHER BOILING MATERIAL. 